Proton conductor, process for producing the same, and electrochemical device

ABSTRACT

Proton conductors, electrochemical devices employing same and methods of manufacturing same are provided. The proton conductor includes silicon oxide, bronsted acid and a derivative of a carbonaceous material predominantly composed of carbon and proton (H + ) dissociating groups introduced to carbon atoms of the carbonaceous material. The proton conductor is produced by a step of forming a compound predominantly composed of silicon oxide and bronsted acid by a sol-gel method, and a step of mixing the compound with a derivative of a carbonaceous material obtained on introducing proton (H + ) dissociating groups to carbon atoms forming a carbonaceous material predominantly composed of carbon.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This patent application claims priority to Japanese PatentDocument No. 2001-009723 filed on Jan. 18, 2001, the disclosure of whichis herein incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] This present invention relates to a proton conductor, itsmanufacturing method and an electro-chemical device.

[0003] A solid substance through the inside of which migrate ions iscontemplated as a possible material associated with an electro-chemicaldevice enumerated first of all by a cell. Currently, ionic conductors ofa variety of conducting ion species, such as Li⁺, Ag⁺, Cu⁺, H⁺ or F⁻,have been found. In particular, the ionic conductors, having protons(H⁺) as conducting ion species, are expected to be used for a variety ofelectro-chemical devices, such as fuel cells or electrochromic displaydevices, as now explained.

[0004] For example, in the case of a fuel cell, having hydrogen as fuel,a reaction (1):

H₂→2H⁺+2e  (1)

[0005] occurs to yield protons, which protons migrate through anelectrolyte so as to be consumed in an air electrode by a reaction (2):

1/2O₂+2H⁺+2e⁻→H₂O  (2)

[0006] so as to be turned into water and so as to generate anelectro-chemical energy. In this regard, by employing the protonconductor as an electrolyte, it is possible to construct a fuel cellfueled by hydrogen.

[0007] A fuel cell, as an electro-chemical device, obtained byapplication of the proton conductor, is expected to be used as a powersupply for generating relatively large current, such as for a standstilluse or for an electrical car. To this end, it is necessary to constructthe solid electrolyte layer of a larger area. It is noted that one ofthe merits of the electrochromic display device, as an electro-chemicaldevice obtained on application of the proton conductor, is its widefield of view. Since the electrochromic display device does not use apolarization plate, in contradistinction from a liquid crystal displayplate, recognition of an object may be made from a wide angle.

[0008] Among known types of the proton conductors, there are inorganicsubstances, such as, for example, uranyl phosphoric acid hydrates ormolybdo phosphoric acid hydrates, and organic substances, such as, forexample, polymer ion exchange membranes, composed of vinyl fluoridebased polymer with side chains inclusive of perfluorosulfonic acid. Themethod for forming thin films of the inorganic substances may beenumerated by a vapor deposition method and a casting method. However,with the film deposition by the vapor deposition method, not only theproduction cost is high, but also difficulties are encountered inproducing a thin film of a larger area. With the casting method, whichis a method of casting a sol containing the proton conductor on asubstrate and allowing to form a gel to produce a proton conductive thinfilm, a thin film obtained by this method includes fine pores formed onsolvent evaporation. Thus, when the proton conductor is applied to afuel cell, since the active material of the fuel cell is gases, namelyhydrogen and oxygen, for example, these gases are transmitted throughthe pores of the proton conductor gel to lower the power generationefficiency.

[0009] In an inorganic proton conductor, since protons in the crystalwater contribute to conduction, such crystal water tends to be desorbedat elevated temperatures to lower the protonic conductivity.

[0010] As a method for possibly overcoming the aforementioned problem toprepare an electrode layer of a larger area, it has been proposed to adda thermoplastic resin to powders of the solid electrolyte to produce acomposite material. However, if the above-mentioned compound, in whichproton conduction is produced by crystal water, is blended with thethermoplastic resin, hopping movement of protons between crystal watermolecules is impeded by the thermoplastic resin, so that protonicconductivity tends to be lowered.

[0011] Although the ion exchange membrane is meritorious in that amembrane with a large area that may be processed readily, may beproduced, such ion exchange membrane is costly at present and hence ithas been desired to develop a proton conductor at lower cost. Moreover,since the ion exchanger resin exhibits high ionic conductivity onlyunder a condition of high water content (tens of %), it suffers from adeficiency that, when the resin is dried, its protonic conductivity islowered.

[0012] For overcoming the aforementioned problem inherent in the protonconductor, the proton conductors disclosed in Japanese Laying-OpenPatent Publications H-8-249923, H-10-69817 and H11-203936 areconstituted by a compound predominantly composed of silicon oxide andbronsted acid, an organic polymer having a thermoplastic elastomer or asulfonic group as a side chain, or a mixture of sulfonides of blockcopolymers made up of a conjugated diene unit and an aromatic vinylunit.

[0013] Although the proton conductor composed of a mixture of thecompound composed substantially of silicon oxide and bronsted acid and avariety of polymers is improved to some extent with the techniquedisclosed in particular in Japanese Laying-Open Patent PublicationH-10-69817. However, there still remains a problem that the protonconductor is inferior in molding or processing performance due to forexample film hardening.

[0014] On the other hand, the protonic conductivity of the protonconductor composed of the aforementioned mixture is changed with thedegree of sulfonation of the polymer making up the mixture. Since thesulfonation degree of the polymer is limited by the type of the monomersmaking up the polymer, the number of sulfonic groups of the polymer isnot enough to form an optimum proton conductor layer in the boundary tothe compound composed predominantly of silicon oxide and bronsted acid,thus raising difficulties in connection with achieving high protonicconductivity.

[0015] A need therefor exists to provide improved proton conductors,methods of manufacturing same and electrochemical devices that employsame.

SUMMARY OF THE INVENTION

[0016] In an embodiment, the present invention provides a protonconductor including silicon oxide, bronsted acid and a derivative of acarbonaceous material substantially composed of carbon and proton (H⁺)dissociating groups introduced to carbon atoms of the carbonaceousmaterial.

[0017] In am embodiment, the present invention provides a method forproducing a proton conductor including a step of forming a compoundpredominantly composed of silicon oxide and bronsted acid by a sol-gelmethod, and a step of mixing this compound with a derivative of acarbonaceous material obtained on introducing proton (H⁺) dissociatinggroups to carbon atoms forming a carbonaceous material predominantlycomposed of carbon.

[0018] In the present invention, the term “proton (H⁺) dissociatinggroups” and/or other like terms means functional groups from whichprotons may be desorbed on electrical dissociation, and “protondesorption” and/or other like terms means separation of protons from thefunctional groups on electrical dissociation.

[0019] According to an embodiment of thepresent invention, a sufficientamount of proton dissociating groups as compared to that introduced toother carbonaceous materials having a polymer material as a skeleton canbe introduced, so that an optimum proton conductor layer may be formedon an interface between silicon oxide, bronsted acid and the derivativeof the carbonaceous material. Consequently, the proton conductoraccording to an embodiment of the present invention, employing siliconoxide and bronsted acid, has a high mobile ion concentration. Inaddition, the proton conductor according to an embodiment of the presentinvention, containing the derivative of the carbonaceous material, isable to realize high protonic conductivity.

[0020] Since the present invention employs a derivative of thecarbonaceous material, composed substantially of carbon, as aconstituent material of the proton conductor, the proton conductoraccording to an embodiment the present invention may operate in a lowhumidity atmosphere, such that its protonic conductivity is not loweredeven in a dry atmosphere.

[0021] Since the derivative of the carbonaceous material is not apolymer, the proton conductor according to an embodiment of the presentinvention is subjected to mechanical interaction with the silicon oxideto a lesser extent than a proton conductor having the polymer as askeleton. The proton conductor of the present invention thereforeremains flexible while it retains high ionic conductivity so that it issuperior in film-forming properties and in workability.

[0022] The electro-chemical device in an embodiment includes a firstelectrode, a second electrode and an electrolyte electrically contactedwith the first and second electrodes, wherein the electrolyte iscomposed of silicon oxide, bronsted acid and a derivative of acarbonaceous material including proton (H⁺) dissociating groupsintroduced to carbon atoms of the carbonaceous material substantiallycomposed of carbon.

[0023] The electro-chemical device according to an embodiment of thepresent invention, in which the electrolyte electrically contacted withthe first and second poles is composed of silicon oxide, bronsted acidand a derivative of the carbonaceous material, achieves favorableeffects similar to those proper to the proton conductor of the presentinvention, and hence is superior in current density and outputcharacteristics.

[0024] Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the figures.

BRIEF DESCRIPTION OF THE FIGURES

[0025]FIGS. 1A and 1B illustrate the structures of fullerenepolyhydroxide as a derivative of a carbonaceous material according to anembodiment of the present invention.

[0026]FIG. 2 shows various carbon clusters as a matrix in the protonconductor according to an embodiment of the present invention.

[0027]FIG. 3 shows carbon clusters (partial fullerene structure) as amatrix in the proton conductor according to an embodiment of the presentinvention.

[0028]FIG. 4 shows carbon clusters (diamond structure) as a matrix inthe proton conductor according to an embodiment of the presentinvention.

[0029]FIG. 5 shows carbon clusters (clusters linked together) as amatrix in the proton conductor according to an embodiment of the presentinvention.

[0030]FIGS. 6A and 6B show fullerene derivatives as a matrix in theproton conductor according to an embodiment of the present invention.

[0031]FIG. 7 is a schematic view showing the structure of a fuel cellaccording to an embodiment of the present invention.

[0032]FIG. 8 is a graph showing a voltage-current curve of a fuel cellaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention generally relates to proton conductors,electrochemical devices employing same, and methods of manufacturingsame. The present invention is described below in greater detail withreference to certain preferred embodiments thereof.

[0034] As bronsted acid, used in the present invention, phosphoric acid(H₃PO₄) or its derivatives, perchloric acid (HClO₄) or its derivatives,are preferably employed according to an embodiment. It should beappreciated that other suitable bronsted acids and mixture thereof canbe employed.

[0035] Silicon oxide may be represented by the following generalformula:

SiO_(x)(1≦x≦2)  (1).

[0036] Silicon oxide contain —OH groups as surface terminal groups. Itis protons of these —OH groups that contribute to ionic conduction. Byfurther adding bronsted acid to the silicon oxide, this type of acidoperates as proton donors to silicon oxide to raise the concentration ofmobile ions, so that the proton conductor of the present inventionexhibits high protonic conductivity.

[0037] If a derivative of a carbonaceous material, obtained onintroducing proton dissociating groups into a carbonaceous material,composed substantially of carbon, is interposed in silicon oxide andbronsted acid, protons desorbed on electrical dissociation from the —OHgroups of the silicon oxide are able to migrate via the protondissociating groups of the derivative of the carbonaceous material, suchthat the derivative of the carbonaceous material contributes to protonicconduction. Thus, with the proton conductor of the present invention, aproton conductor layer is formed on an interface between the siliconoxide, bronsted acid and the carbonaceous material that can exhibit asuperior proton conduction performance.

[0038] Since the derivative of the carbonaceous material is not apolymer, the proton conductor according to an embodiment of the presentinvention is subjected to mechanical interaction with silicon oxide to alesser extent than a proton conductor having the polymer as a skeleton,and remains flexible as it retains high ionic conductivity. On the otherhand, the proton conductor of the present invention can be moldedwithout employing a solvent and is superior in workability.

[0039] The proton conductor, employing silicon oxide, known in the art,may be enumerated by silica gel carrying sulfuric acid on its surface.On the other hand, the proton conductor according to an embodiment ofthe present invention is not simply carrying an acid on its surface, butis a compound of a silicon oxide and bronsted acid because the positionof the IR absorption spectrum associated with to the —OH group ischanged depending on the concentration of the bronsted acid.

[0040] If a substance which produces protonic conduction by crystalwater is used, protonic conductivity is lowered in a dry atmosphere byloss of crystal water in known proton conductor material, as discussedabove. Conversely, with the proton conductor according to an embodimentof the present invention, protonic conduction occurs about the —OHgroup, bonded to the surface of the silicon oxide, as the center. The—OH group, thus chemically combined, is not likely to be desorbed evenin a dry atmosphere, so that it is possible to prevent the protonicconductivity from being lowered subject to such conditions. Moreover,the proton conductor of the present invention, containing theaforementioned derivative of the carbonaceous material, is able tooperate optimally in a dry atmosphere, to prohibit the protonicconductivity from being lowered.

[0041] It is noted that phosphoric acid (H₃PO₄) as bronsted acid is atrivalent bronsted acid and, if the proton conductor according to anembodiment of the present invention is synthesized using this acid, theproton concentration is high, such that a proton conductor having higherionic conductivity may be obtained. For this reason, phosphoric acid orits derivative is preferably employed. On the other hand, the perchloricacid (HClO₄), as bronsted acid, has a strong action as a proton donor,so that, if this bronsted acid is used as the dopant for silicon oxide,the proton conductor synthesized according to the present invention hasa higher protonic conductivity. For this reason, perchloric acid is usedmost preferably as bronsted acid, in addition to phosphoric acid.

[0042] The compound substantially composed of silicon oxide and bronstedacid, as synthesized by the sol-gel method, has a large surface area.Moreover, since the majority of —OH groups, bonded to silicon oxide maybe present on the surface of silicon oxide, the density of —OH groupsmay be higher, as a result of which the proton conductor according tothe present invention may be superior in protonic conductivity. On theother hand, the proton conductor of the present invention, obtained bythe manufacturing method of the present invention may be formed rathereasily into a thin film of a larger area, and hence may be preferablyused as an electrolyte for an electro-chemical device.

[0043] It is desirable that a compound substantially composed of siliconoxide and bronsted acid is formed and that the ratio of this compound tothe derivative of the carbonaceous material by weight is (1:1) to(100:1). If the amount of the derivative of the carbonaceous material istoo small, the protonic conductivity may effectively not be improved. Ifconversely the amount of the derivative of the carbonaceous material istoo large, the proton supply source may effectively be decreased.

[0044] In the carbonaceous material, as the matrix, used in the protonconductor according to an embodiment of the present invention, anysuitable material may be used, provided that the material used ispredominantly composed of carbon. It is however preferred that, afterthe proton dissociating groups have been introduced, the ionicconductivity is desirably higher than electronic conductivity.

[0045] As the carbonaceous material, as the matrix, carbon clusters, asflocculated carbon atoms, or a carbonaceous material, containingtube-like carbonaceous material, may specifically be used. It is howeverpreferred that the carbonaceous material is composed predominantly offor example carbon clusters. The carbonaceous material may also becomposed of carbon clusters.

[0046] The cluster is an aggregate of several to hundreds of atomsbonded or flocculated together. By this aggregation or flocculation,protonic conductivity may be improved, while chemical properties may bemaintained in stability. The “cluster composed predominantly of carbon”and/or other like terms including “cluster composed substantially ofcarbon” means an aggregate formed by several to hundreds of carbonatoms, regardless of the type of carbon-carbon bonds. It should be notedthat the cluster need not be composed only of carbon atoms, but otheratoms may also be present together. The aggregate in which carbon atomsaccount for the major portion is termed a carbon cluster.

[0047] Since the proton conductor according to an embodiment of thepresent invention is composed of a carbonaceous derivative, made up of acarbon cluster as a carbonaceous material, and proton dissociatinggroups, introduced thereto, protons tend to be electrically dissociatedeven in a dry state. So, the proton conductor according to an embodimentof the present invention is superior in protonic conductivity and is notlowered in protonic conductivity even in a dry atmosphere but maintainsits high conductivity such that it remains to be superior infilm-forming properties and in workability. Moreover, since a varietyand number of types of carbonaceous materials are composed in the carboncluster, there is a wide latitude of selection of the carbonaceousmaterial.

[0048] The reason why the carbon cluster is used in this case as thematrix is that, for achieving optimum protonic conductivity, a largequantity of proton dissociating groups need to be introduced, which isrendered possible by the carbon cluster. Although this appreciablyincreases the acidity of the solid proton conductor, the carbon clusteris not susceptible to oxidative deterioration, in distinction from othercarbonaceous materials, and is superior in durability, while constituentatoms are bonded tightly to one another, so that, if acidity is thathigh, there is no risk of interatomic bondage being collapsed, that ischemical change is not likely to be produced, and hence the filmstructure is maintained.

[0049] There are a variety of types of carbon clusters, as shown inFIGS. 1 to 6, such that there is a wide latitude of selection for thestarting materials for the derivatives of the carbonaceous materialconstituting the proton conductor according to an embodiment of thepresent invention. The carbon cluster preferably includes fullerenemolecules, a fullerene structure at least a portion of which has openends, and a diamond structure and combinations thereof.

[0050] Although there is no limitation to the fullerene molecules as acarbon cluster, provided that they are spherical cluster molecules. Inan embodiment, fullerene molecules that include C₃₆, C₆₀ (see FIG. 2),C₇₀ (see FIG. 2), C₇₆, C₇₈, C₈₀, C₈₂ and C₈₄, may desirably be usedeither singly or as a mixture.

[0051] These fullerene molecules were found in 1985 in the mass analysisspectrum of a cluster beam by laser ablation of carbon (Kroto, H. W.;Heath, J. R.; O'Brien, S. C.; Curl, R. F.; Smalley, R. E. nature1985.318, 162). It is five years later that the manufacturing method wasactually established. That is, the manufacturing method by arc dischargeof a carbon electrode was found out in 1990 and, since that time,fullerene attracted attention as a carbonaceous semiconductor material.

[0052] The present inventors conducted research into protonicconductivity of derivatives of the fullerene molecules, and found thatfullerene polyhydroxide, obtained on introducing hydroxy groups to theconstituent carbon atoms of fullerene exhibit high protonic conductivityfor a wide temperature range centered about the ambient temperaturerange, that is a temperature range encompassing the freezing temperatureand the boiling temperature of water (at least from 160° C. to −40° C.),even in a dry condition. The present inventors have also found that, ifhydrogen sulfate groups (ester) are introduced, in place of hydroxygroups, to the constituent carbon atoms of fullerene, it is possible torealize more pronounced protonic conductivity.

[0053] More specifically, fullerene polyhydroxide includes a compoundcomposed of fullerene, to which a number of hydroxy groups are attachedas shown in FIGS. 1A and 1B, and is routinely termed fullerenol.Synthesis examples for fullerenol were first reported by Chiang et al in1992 (Chiang, L. Y.; Swirczewski, J. W.; HSU, C. S.; Chowdhury, S. K.;Cameron, S; Creegan, K. J. Chem, Soc, Chem. Commun. 1992, 1791). Sincethat time, fullerenol into which an amount in excess of a preset amountof hydroxy groups have been introduced has attracted attention inparticular as to its being water-soluble, and has been investigatedpredominantly in the bio-related technical field.

[0054]FIG. 2 shows a variety of carbon clusters, made up of a largenumber of carbon atoms, and which are provided with a closed surfacestructure of a spherical, spheroidal or similar structure. It is notedthat molecular fullerene is also shown.

[0055]FIG. 3 shows a variety of carbon clusters having partiallydefective spherical structures. In these cases, characteristic open endsare present in the structure. Such structures are often observed asby-products in the fullerene manufacturing process employing arcdischarge, and exhibit reactivity proper to fullerene, while alsoexhibiting still higher reactivity in the defective portions, that is inthe open portions. The result is that, by e.g., acid processing,introduction of the acid dissociating substituents (proton dissociatingsubstituents) is accelerated to achieve a higher rate of substituentintroduction and a higher protonic conductivity. Moreover, the carboncluster can be synthesized in larger quantities at exceedingly low cost.

[0056] On the other hand, if the majority of carbon clusters areSP3-bonded, various types of clusters of a diamond structure, such asshown in FIG. 4, can be obtained.

[0057] The aforementioned carbon cluster, the major portions of carbonatoms of which are SP2 bonded, has a graphitic planar structure, or hasthe structure of all or part of fullerene or nanotubes. Of these, thecarbon cluster having a graphitic structure in many cases exhibitselectronic conductivity in the cluster. So, this carbon cluster is notdesirable as a carbonaceous material constituting the proton conductorof the present invention.

[0058] Conversely, the SP2 bond of fullerene or nanotube contains SP3bond in its portion and hence does not exhibit electronic conductivity,in many cases, so that it may be preferentially used as theaforementioned carbonaceous material constituting the proton conductoraccording to an embodiment of the present invention.

[0059]FIG. 5 shows structures of various cluster-to-cluster bonds. Thesestructures may similarly be used according to an embodiment of thepresent invention.

[0060] As the carbonaceous material, tubular carbonaceous materials mayalso be used. The tubular carbonaceous materials may be classified intoso-called carbon nanotubes (CNT) with a diameter equal to approximatelyseveral nanometers (nm) or less, typically 1 to 2 nm, and carbonnanofibers (CNF) with a diameter not less than several nm, andoccasionally reaching 1 gm in case of a large-sized structure. Inparticular, there are two known types of CNT, namely a single-walledcarbon nanotube (SWCNT) composed of a single walled tube, and amultiwall carbon nanotube (MWCNT), in which two or more layers areoverlapped concentrically.

[0061] These are of course merely illustrative such that any suitablestructure may be used according to an embodiment of the presentinvention provided that the above requirement that ionic conductivitybecomes higher than the electronic conductivity following introductionof the proton dissociating groups, is satisfied.

[0062] According to an embodiment of the present invention, it isnecessary that the above-mentioned proton dissociating groups beintroduced to the carbon atoms making up the carbon cluster. As formeans for introducing the proton dissociating groups, the followingmanufacturing method is desirable.

[0063] That is, a carbon cluster composed of carbon powders is firstprepared by arc discharge of a carbonaceous electrode and processed withan acid, such as with a sulfuric acid. The resulting product may furtherbe hydrolyzed or sulfonated or formed into phosphoric acid ester toproduce the derivative of the carbonaceous material as a target product.

[0064] The proton dissociating groups is represented by the formula —XH,where X is any optional bivalent atom or atom group, or by the formula—OH or —YOH, where Y is any optional bivalent atom or atom group.

[0065] For example, the groups that are able to dissociate protons can—COOH, —SO₃H or —OPO(OH)₂, in addition to —OH or —OSO₃H and suitablecombinations thereof.

[0066] The present inventors first found out that, if for examplefullerenol as a derivative of a carbonaceous material and silicon oxideare bonded together, along with bronsted acid, as shown schematically inFIG. 6A, and the resulting product is pressured to form a film increasedin fullerenol density, so that interaction will be produced betweenhydroxy groups of neighboring fullerenol molecules, indicated by ◯ inthe drawing, the resulting flocculated product exhibits high protonicconductivity as a macroscopic aggregate, in other words, high H⁺dissociation characteristics from the phenolic hydroxy groups of thefullerenol molecules, at the same time as its permeation prohibitingperformance for gases, such as hydrogen gas, is improved. In FIGS. 6Aand 6B, the white portions indicate silicon oxide or bronsted acidforming the proton conductor according to an embodiment of the presentinvention, hereinafter the same.

[0067] More specifically, such a film is preferentially used which isobtained on bonding fullerene having a number of —OSO₃H groups, inaddition to fullerenol, with silicon oxide and bronsted acid. Fullerenepolyhydroxide, shown in FIG. 6B, in which the OSO₃H group is substitutedfor the OH group, as shown in FIG. 6B, that is fullerenol in the form ofhydrogen sulfate (ester), was equally reported by Chiang et al., in 1994(Chiang, L. Y.; Wang, L. Y.; Swirczewski, J. W.; Soled, S.; Cameron, S.,J. org. Chem. 1994, 59, 3936). It is possible for fullerene in the formof hydrogen sulfate (ester) to contain only one OSO₃H group in onemolecule, or to contain a plural number each of the latter groups andhydroxy groups.

[0068] As for the protonic conductivity exhibited by flocculation of acertain quantity each of silicon oxide, bronsted acid and the derivativeof the carbonaceous material, as a bulk material, those protons derivedfrom a large quantity of hydroxy groups or OSO₃H groups inherentlycontained in a molecule, are directly involved in migration, so thatthere is no necessity of taking hydrogen or protons derived from steammolecules from the atmosphere, nor of absorbing the moisture fromoutside, in particular from outside air, such that there is imposed noconstraint on the atmosphere. Moreover, it may be contemplated that theaforementioned carbonaceous material in particular exhibitselectrophilic properties, this appreciably contributing to promotion ofelectrical dissociation of hydrogen ions not only from the OSO₃H groupsof high acidity but also from hydroxy groups. This is believed tocontribute to the enhanced protonic conductivity of the proton conductoraccording to an embodiment of the present invention.

[0069] Moreover, since rather large quantities of hydroxy groups orOSO₃H groups can be introduced to for example one fullerene molecule asthe derivative of the carbonaceous material, the number density per unitweight of the conductor of protons taking part in the conduction issignificantly increased. This isalso believed to contribute to enhancedproton conductivity of the proton conductor according to an embodimentof the present invention.

[0070] Since the major portions of the derivative of the carbonaceousmaterial are constituted by carbon atoms, it is lightweight and ishardly susceptible to transmutation. Moreover, it is rather clean and isfree of pollutants that may effect protonic conductivity.

[0071] In addition, in the aforementioned derivative of the carbonaceousmaterial, the number of carbon atoms exposed to the front side is largerthan that of the bulk carbonaceous material, so that the number of sitesto which can be introduced the aforementioned proton dissociating groupsis increased, as a result of which the derivative of the carbonaceousmaterial may have numerous proton dissociating groups on its surface.

[0072] Any of the aforementioned derivatives of the carbonaceousmaterial exhibits high protonic conductivity in a dry state tocontribute to increasing the proton conduction performance of the protonconductor of the present invention.

[0073] The proton conductor in an embodiment of the present inventioncan directly be pressure-molded to a film or a pellet without using abinder. Alternatively, a binder may be used, in which case the protonconductor according to an embodiment of the present invention, having asufficient strength, may be formed.

[0074] The polymer material usable as the binder may be one or more ofknown polymers exhibiting film-forming properties. The amount of mixingof the binder in the proton conductor of the present invention isusually not higher than 20 wt %, because the content in excess of 20 wt% tends to lower the conductivity of hydrogen ions.

[0075] The use of the binder affords film-forming properties, ascribableto the polymer material, to the proton conductor, such that the protonconductor may be used as a pliable ion conducting thin film, with athickness usually not larger than 30 μm, higher in strength than aproduct molded by powder compaction of the silicon oxide, bronsted acidand the derivative of the carbonaceous material, and having theperformance of prohibiting gas transmission.

[0076] It should be appreciated that, there is no limitation to thepolymer material provided that the polymer material used impedesconductivity of hydrogen ions (such as by reaction with the fullerenederivative) to the least extent possible, and exhibits film formingproperties. Usually, such a polymer material is used which does notexhibit electronic conductivity and which exhibits high stability.Specified examples of the high molecular material includepolyfluoroethylene, polyvinylidene fluoride and polyvinyl alcohol thelike and suitable combinations thereof. These are desirable polymermaterials as described below.

[0077] First, polytetrafluoroethylene is desirable because a thin filmof higher strength can be formed more easily with this polymer materialthan with any other polymer material. A small mixing amount of 3 wt % orless and preferably 0.5 to 1.5 wt % suffices, while the thickness of thethin film can be made as thin as 200 μm to 1 μm.

[0078] On the other hand, polyvinylidene fluoride or polyvinyl alcoholis preferred because it gives an ion conductive thin film exhibiting ahigher gas transmission prohibiting performance. The mixing amount inthis case is desirably 5 to 15 wt %.

[0079] The mixing amount of polyfluoroethylene, polyvinylidene fluorideor polyvinyl alcohol lower than the limit value of the above ranges mayaffect film forming.

[0080] For obtaining a thin film in which the proton conductor accordingto an embodiment of the present invention is bonded by the binder, anyknown film forming methods, including pressure molding and extrusionmolding in the first place, may be used.

[0081] The carbon cluster, as a carbonaceous material in the protonconductor according to an embodiment of the present invention, islightweight and insusceptible to transmutation, while being free frompollutants. Moreover, production cost of fullerene is also being loweredprecipitously. Regarding resources, environment and economicaladvantages, carbon clusters as the carbonaceous material may be thoughtof as being a near-ideal carbonaceous material as compared to any othermaterials.

[0082]FIG. 7 shows a fuel cell of an example employing a protonconductor of the present invention according to an embodiment. It isnoted that a catalyst layer 1 of FIG. 7 is a layer of a mixture ofcarbon powders carrying platinum as catalyst, e.g., fluorine basedwater-repellent resin and a pore-forming agent (CaCO₃). The anode 2, asthe first pole, and the cathode 3, as the second pole, are porousgas-diffusing electrodes, each made up of the catalyst layer 1 and, forexample, a carbon sheet as a porous gas-transmitting aggregate 4.Between the anode 2 and the cathode 3 is sandwiched the proton conductoraccording to the present invention.

[0083] This fuel cell includes an anode 2 (fuel pole or hydrogen pole)and a cathode (oxygen pole) 3, facing each other and fitted withterminals 5 and 6, respectively. An ion conduction unit 7 composed of aproton conductor of the present invention is sandwiched between thesetwo poles. In use, hydrogen is passed through an H₂ channel 8. As thefuel (H₂) is passed through the channel 8, hydrogen ions are generated,with which the fuel migrates towards the cathode 3 to react with oxygen(air) passing through an O₂ channel 9, whereby the desired electromotiveforce is taken out.

[0084] Meanwhile, the H₂ channel 8 and the O₂ channel 9 are constructedin separators 10, 11 formed of channel-shaped graphite.

[0085] This fuel cell has, as its electrolyte, a proton conductor, whichis made up by silicon oxide, bronsted acid and a derivative of thecarbonaceous material, in accordance with the teaching of the presentinvention. By employing silicon oxide and bronsted acid, theconcentration of mobile ions is higher and, by further employing thederivative of the carbonaceous material, a higher protonic conductivitycan be achieved.

[0086] Since the derivative of the carbonaceous material, composedpredominantly of carbon, is used as a constituent material for theproton conductor, the proton conductor also operates in a low humidityatmosphere, so that protonic conductivity is not lowered even in a dryatmosphere.

[0087] The derivative of the carbonaceous material is not a polymermaterial, so that mechanical interaction thereof with silicon oxide isless than in case the derivative of the carbonaceous material includesthe polymer as the skeleton. The proton conductor of the presentinvention therefore remains flexible while it retains high ionicconductivity so that it is superior in film-forming properties and inworkability.

[0088] Since hydrogen ions are desorbed in the anode 2 and, as hydrogenions are desorbed in the ion conduction unit 7, the hydrogen ionssupplied from the anode 2 migrate towards the cathode 3, hydrogen ionconductivity is characteristically high, with the result that the systemcan be simplified in structure and lightweight, while it is possible toimprove such functions as current density of output characteristicsfurther.

[0089] In place of the ion conduction unit 7, which is composed only ofthe film-shaped proton conductor, according to an embodiment of thepresent invention, obtained on pressure molding silicon oxide, bronstedacid and the derivative of the carbonaceous material, and which issandwiched between the first and second poles, a proton conductor bondedby a binder according to the present invention may also be used as theion conduction unit 7. In such case, the ion conduction unit 7 bonded bythe binder and hence having a sufficient strength may be formed.

[0090] The present invention is hereinafter explained more specificallywithout limitations based on Examples of the present invention accordingto an embodiment.

EXAMPLE 1

[0091] In the present Example 1, a proton conductor is fabricated usingsilica gel doped with phosphoric acid, as a compound composedpredominantly of silicon oxide and bronsted acid, and also using afullerene derivative, obtained on introducing hydroxy groups intofullerene (routinely termed fullerenol) as the derivative of thecarbonaceous material comprised of a carbonaceous material composedpredominantly of carbon into which have been introduced protondissociating groups.

[0092] The silica gel, doped with phosphoric acid, was synthesized bythe following method. As a starting material for synthesizing silicagel, tetraethoxysilane (TEOS) diluted in ethanol was used. TheTEOS/ethanol mixing molar ratio was set to 1:4. To this solution wereadded pure water, in an amount by a molar ratio of 8 with respect toTEOS, a 3.6 wt % aqueous solution of hydrochloric acid which will givean amount of HCl in a molar ratio of 0.01 with respect to TEOS andtetraethyl ammonium tetrafluoroborate in an amount by a molar ratio of0.01 with respect to TEOS, and the resulting mass was stirred for fiveminutes. A 85 wt % aqueous solution of phosphoric acid then was added inan amount which resulted in TEOS:H₃PO₄ [ ]equaling 1:0.5 and theresulting mass was stirred for three hours in a hermetically sealedvessel. The resulting mixture was then allowed to stand for five hoursfor gelation and dried at 60° C. for two hours under a reduced pressure,to yield silica gel doped with phosphoric acid. The silica gel dopedwith phosphoric acid obtained as described above was then pulverized andstirred in NMP (1-methyl-2-pyrrolidone) in which for example (C₆₀(OH)₁₂) was dispersed. The weight ratio of the silica gel to fullerenolwas set to 20:1. Finally, NMP was vaporized off under agitation toproduce the proton conductor according to the present invention.

[0093] The ionic conductivity of the proton conductor, obtained asdescribed above, was measured by the following method. 200 mg of theproton conductor, obtained by the above method, were pressure-molded toa disc-shaped pellet, 10 mm in diameter, and a gold foil was pressurebonded to both surfaces of the pellet to form electrodes for measuringthe electrical conductivity. Using an electro-chemical cell, prepared asdescribed above, the electrical conductivity of the proton conductor wasmeasured at room temperature. As a result, the ionic conductivityindicated a value of 2.0×10⁻³ S/cm. This proton conductor was stored forten days in a desiccator charged with diphosphorus pentoxide as a drierand measurement was made of electrical conductivity thereof. It wasfound that conductivity was scarcely lowered. According to an embodimentof the present invention, as described above, it was found that suchproton conductor can be obtained exhibiting high ionic conductivitywhich is effectively not lowered even in a dry atmosphere. The film isextremely pliable such that no problem was raised in molding the film toa desired shape.

COMPARATIVE EXAMPLE

[0094] A film was formed in the same way as in Example 1, using a protonconductor to which sulfonated polyisopropylene was mixed in place offullerenol. Although the value of the order of 10⁻³ to 10 ⁻⁴ S/cm couldbe obtained in measurement, the film was rather hard such that it wasextremely difficult to mold the film to a desired shape.

EXAMPLE 2

[0095] In the present Example, a proton conductor was synthesized in thesimilar manner as in Example 1, except employing perchloric acid inplace of phosphoric acid as the bronsted acid. In the same way as inExample 1, TEOS diluted with ethanol was added to with pure water,hydrochloric acid and perchloric acid in this order. At this time, theamounts of TEOS, ethanol, pure water and hydrochloric acid were to setto a molar ratio of 1:8:4:0.05. To this solution was added such anamount of perchloric acid which is equal 20 wt % based on the weight ofsilica gel, doped with perchloric acid, which may be estimated to beproduced. The resulting solution was stirred at room temperature forthree hours and allowed to stand for five hours to form a gel. Finally,the resulting gel was dried under reduced pressure at 60° C. for twohours to produce a silica gel doped with perchloric acid. To the soproduced silica gel, doped with perchloric acid, NMP in which wasdispersed fullerenol was added to give a fullerenol to silica gel weightratio of 1:50. The resulting mass was stirred to vaporize off NMP toproduce the proton conductor. In forming the film, no such problem asoccurred in the above-described Comparative Example was encountered.

[0096] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 2.5×10⁻² S/cm. The value ofconductivity was not seen to be lowered even when the proton conductorwas stored in a dry atmosphere. It may therefore be seen that, with thepresent invention, there may be obtained a proton conductor which issatisfactory in film forming properties and workability, indicates ahigh ionic conductivity and which is not lowered in ionic conductivityeven under a dry atmosphere.

EXAMPLE 3

[0097] In the present Example, a proton conductor was synthesized in thesame way as in Example 2, except employing, as bronsted acid, phosphorustungstic acid (H₃PW₁₂O₄₀.29H₂O), as a phosphoric acid derivative, inplace of hydrochloric acid. It is noted that phosphorus tungstic acidwas added to the mixed solution of TEOS, ethanol, pure water andhydrochloric acid so that the weight of phosphorus tungstic acid will be45% of the weight of silica gel, doped with phosphorus tungstic acid,which is estimated to be produced. To the so produced silica gel, dopedwith perchloric acid, NMP in which was dispersed fullerenol was added togive a fullerenol to silica gel weight ratio of 1:70. The resulting masswas stirred to vaporize off NMP to produce the proton conductor. Informing the film, no such problem as occurred in the above-describedComparative Example was encountered.

[0098] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 1.8×10⁻³ S/cm. It may therefore beseen that, with the present invention, there may be obtained a protonconductor which is satisfactory in film forming properties andworkability, and which indicates a high ionic conductivity.

EXAMPLE 4

[0099] In the present Example, a proton conductor was synthesized in thesame way as in Example 3, except employing, as bronsted acid, phosphorusmolybdic acid (H₃PWo₁₂O₄₀.29H₂O), as a phosphoric acid derivative, inplace of hydrochloric acid used in Example 1. In forming the film, nosuch problem as occurred in the above-described Comparative Example wasencountered.

[0100] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 1.5×10⁻³ S/cm. The value ofconductivity was not seen to be lowered even when the proton conductorwas stored in a dry atmosphere. It may therefore be seen that, with thepresent invention, there may be obtained a proton conductor which issatisfactory in film forming properties and workability and whichindicates a high ionic conductivity.

EXAMPLE 5

[0101] In the present Example, a proton conductor was synthesized in thesame way as in Example 3, except employing silicon isopropoxide, as astarting material yielding silicon oxide, in place of TEOS used inExample 1. In forming the film, no such problem as occurred in theabove-described Comparative Example was encountered.

[0102] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 1.2×10⁻³ S/cm. The value ofconductivity was not seen to be lowered even when the proton conductorwas stored in a dry atmosphere. It may therefore be seen that, with thepresent invention, there may be obtained a proton conductor which issatisfactory in film forming properties and workability, indicates ahigh ionic conductivity and which is not lowered in ionic conductivityeven in a dry atmosphere.

EXAMPLE 6

[0103] In the present Example, a proton conductor was obtained in thesame way as in Example 1 except changing the amount of fullerenol, as aderivative of the carbonaceous material, into the carbonaceous materialof which, predominantly composed of carbon, proton dissociating groupshave been introduced. The silica gel, doped with phosphoric acid, wassynthesized in the same way as in Example 1. To this silica gel wasadded NMP in which was dispersed fullerenol to give a fullerenol tosilica gel weight ratio of 1:50. The resulting mass was stirred tovaporize off NMP to produce the proton conductor. In forming the film,no such problem as occurred in the above-described Comparative Examplewas encountered.

[0104] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 4.0×10⁻³ S/cm. It may therefore beseen that, with the present invention, there may be obtained a protonconductor which is satisfactory in film forming properties andworkability, indicates a high ionic conductivity and which is notlowered in ionic conductivity even in a dry atmosphere.

EXAMPLE 7

[0105] In the present Example, a proton conductor was synthesized in thesame way as in Example 1, except employing, as a derivative of thecarbonaceous material, into the carbonaceous material of whichpredominantly composed of carbon are introduced proton dissociatinggroups, fullerenol in the form of hydrogen sulfate (ester) obtained onhydrogen sulfate esterification of hydroxy groups (C₆₀(OSO₃H)₁₂) inplace of hydrochloric acid used in Example 1. In forming the film, nosuch problem as occurred in the above-described Comparative Example wasencountered.

[0106] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 3.3×10⁻² S/cm. The value ofconductivity was not seen to be lowered even when the proton conductorwas stored in a dry atmosphere. It may therefore be seen that, with thepresent invention, there may be obtained a proton conductor which issatisfactory in film forming properties and workability, indicates ahigh ionic conductivity and which is not lowered in ionic conductivityeven in a dry atmosphere.

EXAMPLE 8

[0107] In the present Example, a proton conductor was synthesized in thesame way as in Example 3, except employing sulfonated fullerene(C₆₀(SO₃H)₁₂) in place of fullerenol used in Example 1. In forming thefilm, no such problem as occurred in the above-described ComparativeExample was encountered.

[0108] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 3.5×10⁻² S/cm. The value ofconductivity was not seen to be lowered even when the proton conductorwas stored in a dry atmosphere. It may therefore be seen that, with thepresent invention, there may be obtained a proton conductor which issatisfactory in film forming properties and workability, indicates ahigh ionic conductivity and which is not lowered in ionic conductivityeven in a dry atmosphere.

EXAMPLE 9

[0109] In the present Example, a proton conductor was synthesized in thesame way as in Example 1, except employing sulfonated carbon soot, inplace of fullerenol used in Example 1, as a derivative of thecarbonaceous material, into the carbonaceous material of whichpredominantly composed of carbon are introduced proton dissociatinggroups. In this case, carbon soot which is obtained in addition tofullerene in producing fullerene by arc discharge and which is processedin the presence of fuming sulfuric acid, is used as a mixing ingredient.In forming the film, no such problem as occurred in the above-describedComparative Example was encountered.

[0110] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 1.5×10⁻² S/cm. It may therefore beseen that, with the present invention, there may be obtained a protonconductor which is satisfactory in film forming properties andworkability, indicates a high ionic conductivity and which is notlowered in ionic conductivity even in a dry atmosphere.

EXAMPLE 10

[0111] In the present Example, a proton conductor was synthesized in thesame way as in Example 1, except employing a sulfonated fullerenepolymer in place of hydrochloric acid used in Example 1, as a derivativeof the carbonaceous material, into the carbonaceous material of whichpredominantly composed of carbon are introduced proton dissociatinggroups. The fullerene polymer was obtained on firing fullerene powdersat 1000° C. for one hour, in an argon atmosphere, using iron as acatalyst. Sulfonation was by processing in the presence of fumingsulfuric acid. In forming the film, no such problem as occurred in theabove-described Comparative Example was encountered.

[0112] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 1.8×10⁻² S/cm. The value ofconductivity was not seen to be lowered even when the proton conductorwas stored in a dry atmosphere. It may therefore be seen that, with thepresent invention, there may be obtained a proton conductor which issatisfactory in film forming properties and workability, indicates ahigh ionic conductivity and which is not lowered in ionic conductivityeven in a dry atmosphere.

EXAMPLE 11

[0113] In the present Example, a proton conductor was synthesized in thesame way as in Example 1, except employing, in place of fullerenol usedin Example 1, a sulfonated carbonaceous material, containing a diamondstructure, as a derivative of the carbonaceous material, into thecarbonaceous material of which predominantly composed of carbon areintroduced proton dissociating groups. The carbonaceous material wasobtained by the CVD (chemical vapor deposition) method and powders soformed were processed in the presence of fuming sulfuric acid forsulfonation. In forming the film, no such problem as occurred in theabove-described Comparative Example was encountered.

[0114] The ionic conductivity of the so produced proton conductor wasmeasured in the same way as in Example 1. As a result, the ionicconductivity indicated a value of 4.8×10⁻⁴ S/cm. On the other hand,conductivity was not seen to be lowered on storage in a dry atmosphere.It was seen from Example 11 above that although a sufficient amount ofsulfone groups comparable to that introduced to other carbonaceousmaterials were occasionally not introduced to the diamond structure, sothat the carbonaceous material of the Example was lowered, such a protonconductor may be obtained in this Example which has good film formingproperties and workability and in which ionic conductivity is notlowered even in a dry atmosphere.

EXAMPLE 12

[0115] In this Example, a fuel cell having a structure shown in FIG. 7was prepared with a proton conductor.

[0116] First, NMP in which was dispersed fullerenol was added to thesilica gel, doped with phosphoric acid, as obtained in Example 1. Theresulting mass was kneaded until it was slurried. The slurried mass thenwas coated on a polyethylene tetrafluoride plate, by a doctor blademethod, to a thickness of 50 μm. After vaporizing off NMP under reducedpressure, the coating was peeled off from the polyethylene tetrafluorideplate to produce an electrolyte layer for the fuel cell. As a gasdiffusion electrode, a carbon electrode carrying platinum in an amountof for example 0.35 mg/cm² was used. The NMP in which was dispersedfullerenol was added to the silica gel, doped with phosphoric acid, togive the mass similar to that used for forming the electrolyte layer forthe fuel cell. The resulting mass was sprayed onto this gas diffusionelectrode and dried under reduced pressure for use as an electrode. Theabove electrolyte layer was sandwiched by two such electrodes andpress-worked at room temperature to prepare a fuel cell device. Usingthe so produced fuel cell device, the fuel cell shown in FIG. 7 wasproduced.

[0117] In conducting a cell test, hydrogen pressurized to 3 atm and airpressurized to 5 atm were sent to an H₂ channel and to an O₂ channel 9,respectively, to check for the relationship between the output currentand the cell voltage. The resulting voltage-current curve is shown inFIG. 8. As may be seen from FIG. 8, the cell voltage was maintained at avalue not lower than 0.6V even when the current of 400 mA/cm² was causedto flow, thus indicating that the fuel cell obtained with the presentembodiment exhibits high output characteristics.

[0118] It may be seen that, with use of the proton conductor accordingto an embodiment of the present invention, fuel cells having superiorcharacteristics can be obtained.

[0119] In the above-described embodiment, description has been made onlywith respect to the use of fullerenol, fullerenol in the form of ahydrogen sulfate (ester) and sulfonated fullerene as a derivative of thecarbonaceous material comprised of the carbonaceous materialpredominantly composed of carbon to which have been introduced theproton dissociating groups. Similar effects may, of course, be obtainedwith use of other derivatives of the carbonaceous materials than thoselisted in the foregoing embodiments. Although the use of phosphoric acidand perchloric acid has been explained as bronsted acid in the foregoingembodiments, similar effects can, of course, be obtained when boricacid, silicic acid or plural species of the bronsted acid are used incombination. That is, the present invention is not limited to thebronsted acids listed in the above-described embodiment.

[0120] Although the description of the above-described embodiment isdirected to the fuel cell as the electro-chemical device of the presentinvention employing the proton conductor of the present invention, thepresent invention can be applied to those electro-chemical devices notexplained in the foregoing embodiment, such as cell, pH sensor and/orthe like. That is, the electro-chemical devices to which the presentinvention is applied are not limited to those explained in theabove-described embodiments.

[0121] As described above, in a carbonaceous material forming theconstituent material of the proton conductor of the present invention inan embodiment, a sufficient amount of proton dissociating groups ascompared to that introduced to other carbonaceous materials having apolymer material as a skeleton can be introduced, so that an optimumproton conductor layer may be formed on an interface between siliconoxide, bronsted acid and the derivative of the carbonaceous material.Consequently, the proton conductor according to an embodiment of thepresent invention, employing silicon oxide and bronsted acid, has a highmobile ion concentration. In addition, the proton conductor according toan embodiment of the present invention, containing the derivative of thecarbonaceous material is able to realize high protonic conductivity.

[0122] Since the present invention uses a derivative of the carbonaceousmaterial, composed predominantly of carbon, as a constituent material ofthe proton conductor, the proton conductor according to the presentinvention may operate in a low humidity atmosphere, such that itsprotonic conductivity is not lowered even in a dry atmosphere.

[0123] Since the derivative of the carbonaceous material is not apolymer material, its mechanical interaction with silicon oxide is lessthan that in case of the carbonaceous materials having a polymermaterial as a skeleton. Consequently, the proton conductor according toan embodiment of the present invention exhibits flexibility whileretaining high ionic conductivity, and is superior in film-formingproperties and workability.

[0124] The electro-chemical device according to an embodiment thepresent invention includes first and second poles and an electrolyteelectrically contacted with these poles, with the electrolyte being aproton conductor composed of silicon oxide, bronsted acid and aderivative of the carbonaceous material. Consequently, theelectro-chemical device according to an embodiment of the presentinvention can exhibit favorable effects similar to those of the protonconductor of the present invention, thus realizing reduction in size anda simpler structure of the system. Moreover, the electro-chemical deviceaccording to an embodiment of the present invention is superior incurrent density and output characteristics.

[0125] It should be understood that various changes and modifications tothe presently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

1. A proton conductor comprising silicon oxide, brensted acid and aderivative of a carbonaceous material predominantly composed of carbonand proton (H⁺) dissociating groups introduced to carbon atoms of saidcarbonaceous material.
 2. The proton conductor according to claim 1wherein said brensted acid is phosphoric acid (H₃PO₄) or derivativesthereof.
 3. The proton conductor according to claim 1 wherein saidbrensted acid is perchloric acid (HClO₄) or derivatives thereof.
 4. Theproton conductor according to claim 1 wherein said silicon oxide isrepresented by the following general formula: SiOx (1≦x≦2)  (1).
 5. Theproton conductor according to claim 1 wherein a compound predominantlycomposed of silicon oxide and brensted acid is formed, this compoundhaving a weight ratio of (1:1) to (100:1) to said derivative of thecarbonaceous material.
 6. The proton conductor according to claim 1wherein said carbonaceous material is predominantly composed of carbonclusters which are aggregates of carbon atoms.
 7. The proton conductoraccording to claim 6 wherein said carbonaceous material is at least oneselected from the group consisting of fullerene molecules, a structurehaving an open end at at least a portion of the fullerene structure anda structure having a diamond structure.
 8. The proton conductoraccording to claim 6 wherein said carbonaceous material is comprised ofsaid carbon clusters coupled together.
 9. The proton conductor accordingto claim 1 wherein said carbonaceous material is carbon nanotubes. 10.The proton conductor according to claim 1 wherein said protondissociating groups are —XH, where X is any optional bivalent atom oratom group and wherein H is a hydrogen atom.
 11. The proton conductoraccording to claim 11 wherein said proton dissociating groups are —OH or—YOH, where Y is any optional bivalent atom or atom group and wherein His a hydrogen atom.
 12. The proton conductor according to claim 11wherein said proton dissociating groups are selected from among —OH,—OSO₃H, —COOH, —SO₃H and —OPO(OH)₂.
 13. The proton conductor accordingto claim 7 wherein said fullerene molecules are molecules of sphericalcarbon cluster molecules C_(m), where m is 36, 60, 70, 76, 78, 80, 82and
 84. 14. A method for the preparation of a proton conductorcomprising: a step of forming a compound predominantly composed ofsilicon oxide and brensted acid by a sol-gel method; and a step ofmixing this compound with a derivative of a carbonaceous materialobtained on introducing proton (H⁺) dissociating groups to carbon atomsforming a carbonaceous material predominantly composed of carbon. 15.The method for the preparation of a proton conductor according to claim14 wherein said brensted acid is phosphoric acid (H₃PO₄) or derivativesthereof.
 16. The method for the preparation of a proton conductoraccording to claim 14 wherein said brensted acid is perchloric acid(HClO₄) or derivatives thereof.
 17. The method for the preparation of aproton conductor according to claim 14 wherein said silicon oxide isrepresented by the following general formula: SiOx (1≦x≦2)  (1).
 18. Themethod for the preparation of a proton conductor according to claim 14wherein a compound predominantly composed of silicon oxide and brenstedacid is formed, this compound having a weight ratio of (1:1) to (100:1)to said derivative of the carbonaceous material.
 19. The method for thepreparation of a proton conductor according to claim 14 wherein saidcarbonaceous material is predominantly composed of carbon clusters whichare aggregates of carbon atoms.
 20. The method for the preparation of aproton conductor according to claim 19 wherein said carbonaceousmaterial is at least one selected from the group consisting of fullerenemolecules, a structure having an open end at at least a portion of thefullerene structure and a structure having a diamond structure.
 21. Themethod for the preparation of a proton conductor according to claim 19wherein said carbonaceous material is comprised of said carbon clusterscoupled together.
 22. The method for the preparation of a protonconductor according to claim 14 wherein said carbonaceous material iscarbon nanotubes.
 23. The method for the preparation of a protonconductor according to claim 14 wherein said proton dissociating groupsare —XH, where X is any optional bivalent atom or atom group and whereinH is a hydrogen atom.
 24. The method for the preparation of a protonconductor according to claim 14 wherein said proton dissociating groupsare —OH or —YOH, where Y is any optional bivalent atom or atom group andwherein H is a hydrogen atom.
 25. The method for the preparation of aproton conductor according to claim 24 wherein said proton dissociatinggroups are selected from among —OH, —OSO₃H, —COOH, —SO₃H and —OPO(OH)₂.26. The method for the preparation of a proton conductor according toclaim 20 wherein said fullerene molecules are molecules of sphericalcarbon cluster molecules C_(m), where m is 36, 60, 70, 76, 78, 80, 82and
 84. 27. An electrochemical device comprising a first electrode, asecond electrode and an electrolyte electrically contacted with saidfirst and second electrodes, wherein said electrolyte is composed ofsilicon oxide, brensted acid and a derivative of a carbonaceous materialincluding proton (H⁺) dissociating groups introduced to carbon atomsmaking up the carbonaceous material predominantly composed of carbon.28. The electro-chemical device according to claim 27 wherein saidbrensted acid is phosphoric acid (H₃PO₄) or derivatives thereof.
 29. Theelectro-chemical device according to claim 27 wherein said brensted acidis perchloric acid (HClO₄) or derivatives thereof.
 30. Theelectro-chemical device according to claim 27 wherein said silicon oxideis represented by the following general formula: SiOx (1≦x≦2)  (1). 31.The electro-chemical device according to claim 27 wherein a compoundpredominantly composed of silicon oxide and brensted acid is formed,this compound having a weight ratio of (1:1) to (100:1) to saidderivative of the carbonaceous material.
 32. The electro-chemical deviceaccording to claim 27 wherein said carbonaceous material ispredominantly composed of carbon clusters which are aggregates of carbonatoms.
 33. The electro-chemical device according to claim 32 whereinsaid carbonaceous material is at least one selected from the groupconsisting of fullerene molecules, a structure having an open end at atleast a portion of the fullerene structure and a structure having adiamond structure.
 34. The electro-chemical device according to claim 32wherein said carbonaceous material is comprised of said carbon clusterscoupled together.
 35. The electro-chemical device according to claim 27wherein said carbonaceous material is carbon nanotubes.
 36. Theelectro-chemical device according to claim 27 wherein said protondissociating groups are —XH, where X is any optional bivalent atom oratom group and wherein H is a hydrogen atom.
 37. The electro-chemicaldevice according to claim 27 wherein said proton dissociating groups are—OH or —YOH, where Y is any optional bivalent atom or atom group. 38.The electro-chemical device according to claim 37 wherein said protondissociating groups are selected from among —OH, —OSO₃H, —COOH, —SO₃Hand —OPO(OH)₂.
 39. The electro-chemical device according to claim 33wherein said fullerene molecules are molecules of spherical carboncluster molecules C_(m), where m is 36, 60, 70, 76, 78, 80, 82 and 84.40. The electrochemical device according to claim 27 wherein the deviceis arranged as a fuel cell, hydrogen or a hydrogen containing gas issupplied to said first pole and wherein oxygen or an oxygen containinggas is supplied to said second pole.